Townsley used his final lifeline, Phone A Friend, but the friend did not know the answer either.

The correct answer was D: Isle Of Man TT.

Andrew Townsley declined to play for £1m but turned out to know the answer. (Stellify Media/ITV)

Townsley told Clarkson: “I don't know the answer and it's just too much money to lose. Having got so far and to go on a whim I think would be foolish and Niagara Falls is looking very nice at this time.”

He later told The Sun: “I was actually 50/50. If I still had the 50/50 lifeline I would have.

“I thought it probably was the TT. But was I prepared to risk it?

“The show went very quick. That was my abiding memory of it. I found myself suddenly running out of questions in no time at all.”

Townsley, who appeared on the show in a wheelchair and has progressive multiple sclerosis (MS), plans to use his £500,000 to pay for a trip to Niagara Falls.

Judith Keppel was the first winner of Who Wants to Be A Millionaire? in 2000. (PA)

Judith Keppel became the first person to win £1m on the show in November 2000, during the quiz show’s eighth series. She went on to become part of a panel of quiz experts on BBC gameshow Eggheads.

Since then there have been five more jackpot winners, the most recent being self-professed quiz expert Ingram Wilcox in 2006.

In 2001, Major Charles Ingram (no relation), his wife Diana and an accomplice, Tecwen Whittock, were accused of cheating their way to £1m.